JP2000301919A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a separation trouble inside a bead part from being generated, so as to enhance durability of the bead part. SOLUTION: A carcass layer 16 winds a terminal part 16C in along an outer circumference of a bead core 12 substantially free from generation of deformation at the time of loaded rotation to prevent a separation trouble of rubber which starts at the terminal part 16C as a start point. A rigid rubber sheet 24 with hardness set at a hardness level higher than that of a rubber for coating a code of a bead core reinforcing layer 18 is arranged in a terminal part 18B side of the layer 18 to be projected to a tire radial-directional outside from the terminal part 18B. Although compressive force is applied onto the terminal part 18B when bending deformation is generated by falling-in of a bead part 11 at the time of loaded rotation, stress concentration in the terminal part 18B is moderated because the rubber sheet 24 receives the compressive force before the compressive force is applied to the terminal part 18B. Separation generated in the terminal part 18B of the bead reinforcing layer 18 as the start point is thereby prevented from being generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire having improved durability of a bead portion.

[0002]

2. Description of the Related Art In a pneumatic radial tire used for trucks and the like, particularly used under heavy load, and after being worn, the tread is rehabilitated and used a plurality of times, a stress concentration portion of a reinforcing cord end of a carcass layer is used by long-term use. There is a problem that separation occurs in the rubber from the starting point and the tire cannot be used.

That is, in a tire used by filling a high internal pressure, such as a tire for a truck or a bus, the carcass layer tends to be pulled out from the bead core by air pressure, and a large stress concentration occurs at the terminal portion. Is repeatedly deformed, thereby causing a separation failure starting from the terminal portion.

In order to cope with such a separation failure at the end of the carcass, conventionally, a bead portion reinforcing layer is arranged outside the carcass layer, and the arrangement of a rubber member at the bead portion is devised (for example, Japanese Patent Laid-Open No. 2-279403). Many technologies have been proposed.

[0005]

In recent years, the use conditions of large tires for trucks and buses have become severer due to an increase in the number of times of rehabilitation in consideration of the environment and economy. In the tire having a low flatness, the durability of the bead deteriorates. Therefore, even if the conventional technique is used, the prevention of the separation failure in the bead portion is not sufficient, and the fundamental solution to the failure of the bead portion has not been reached.

The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic radial tire having excellent bead durability and suitable for heavy-duty vehicles.

[0007]

According to a first aspect of the present invention, there is provided a main body extending from a bead core of one bead to a bead core of the other bead, and a main body provided continuously with the main body. A carcass comprising at least one carcass layer composed of a plurality of steel cords extending substantially in the radial direction having a winding portion wound along an outer peripheral surface, and a carcass provided at a tire radial direction outside of the carcass, A pneumatic radial tire having a belt that reinforces a crown portion of a carcass, comprising a plurality of cords inclined with respect to a radial direction,
A coating provided with a bead reinforcing layer disposed around the bead core outside the tire of the carcass layer, and coating a cord of the bead reinforcing layer on a lateral side of a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction. A hard rubber sheet that is harder than rubber is disposed, and the hard rubber sheet protrudes outward in the tire radial direction from a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction.

Next, the operation of the pneumatic radial tire according to the first aspect will be described.

In the pneumatic radial tire according to the present invention, the carcass layer is formed by plastic deformation and is wound around the outer peripheral surface of the bead core, so that the terminal portion, which is a source of stress concentration, hardly deforms at the time of load rolling. By arranging it on the upper side, the separation failure originating from the terminal portion of the carcass layer is fundamentally eliminated.

In addition, since the bead reinforcing layer is arranged outside the tire of the carcass layer and around the bead core, it is possible to prevent abrasion of the tire outer skin due to friction with the rim flange during rolling.

A terminal portion of the bead reinforcing layer is disposed in the bead portion, and a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction becomes a source of stress concentration similar to the carcass layer terminal portion of the conventional tire.

That is, when the bead portion bends in the rim flange direction during load rolling, the main body portion of the carcass layer radially outward from the vicinity of the end portion of the bead reinforcing layer sinks inward in the tire radial direction. In order to make such a deformation, a large compressive strain is generated in the end portion of the bead reinforcing layer.

At this time, in the arrangement in which the vicinity of the end portion of the bead reinforcing layer is inclined so as to approach the main body portion of the carcass layer, compressive deformation is more likely to occur directly at the end portion.

Here, in the present invention, a hard rubber sheet harder than the coating rubber coating the cord of the bead reinforcing layer is disposed on the side of the end portion of the bead reinforcing layer on the outer side in the tire axial direction. Since the hard rubber sheet is projected outward in the tire radial direction from the terminal portion, the hard rubber sheet receives the compressive force from the tire radial outside before acting on the terminal portion of the bead reinforcing layer, and the bead reinforcing layer Stress concentration at the end of the (cord) is reduced. As a result, it is possible to prevent the separation starting from the end portion of the bead reinforcing layer.

Further, unlike the end portion of the carcass layer, the end portion of the bead reinforcing layer is hardly subjected to the force of being pulled out by the internal pressure. Unlike the folded portions of the carcass layer, which are not adjacent to each other, and the cords are inclined with respect to the radial direction, the cords in the bead reinforcing layer are not By changing the angle, the compressive stress generated at the cord end is relieved and the stress concentration is reduced.However, at the cord end, the stress concentration is not completely eliminated due to the rigidity step between the reinforcing cord and the surrounding rubber. Absent. Therefore, by arranging a hard rubber sheet that is harder than the coating rubber of the bead reinforcing layer so as to cover the end portion of the bead reinforcing layer, the rigidity step of the terminal portion is also reduced, the compressive strain of the terminal portion is reduced, and the durability of the bead portion is improved. The performance is greatly improved. Even when bending deformation of the bead portion occurs at the time of load rolling, the cord in the bead reinforcing layer is hardly changed in angle, and stress concentration at the terminal portion due to the deformation is relieved, so that the terminal portion is moved further out of the tire. The durability of the bead portion is greatly improved by tilting the terminal portion to reduce the compression strain of the terminal portion.

According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the amount of protrusion of the hard rubber sheet from a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction is 25 mm or less. It is characterized by having.

Next, the operation of the pneumatic radial tire according to claim 2 will be described.

If the hard rubber sheet protrudes too far outward in the tire radial direction from the end portion of the bead reinforcing layer, the hard rubber sheet is located on the tire side portion where the bend is large, and serves as a core of the separation. Is preferably 25 mm or less.

According to a third aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the hard rubber sheet is disposed inside the bead reinforcing layer in the tire axial direction. Features.

Next, the operation of the pneumatic radial tire according to claim 3 will be described.

The inside of the bead reinforcing layer in the tire rotation axis direction is
Since it is closer to the carcass layer main body, the influence of the compressive strain due to the fall of the bead is large. By arranging the hard rubber sheet at this position, the stress concentration at the end can be more effectively alleviated.

According to a fourth aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the hard rubber sheet is disposed outside the bead reinforcing layer in the tire axial direction. Features.

Next, the operation of the pneumatic radial tire according to claim 4 will be described.

The outer side of the bead reinforcing layer in the tire rotation axis direction is
Regarding the compressive stress caused by the carcass body falling down,
The effect is small as compared with the inner side in the rotation axis direction, but on the other hand, when the tire outer skin falls down on the rim flange at the time of bead falling down deformation, it is affected by shear strain due to pushing up from the rim flange. Therefore, by reinforcing the outer side of the end portion of the bead reinforcing layer in the tire rotation axis direction with a hard rubber sheet, the shear distortion is suppressed and the durability of the bead portion is improved.

According to a fifth aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the hard rubber sheet is disposed both outside and inside the bead reinforcing layer in the tire axial direction. And the end portion of the bead reinforcing layer on the outer side in the tire axial direction is covered.

Next, the operation of the pneumatic radial tire according to claim 5 will be described.

By arranging the hard rubber sheets both inside and outside the tire rotation axis direction of the end portion of the bead reinforcing layer, both the compression strain due to the carcass body falling down and the shear strain due to pushing up from the rim flange are effectively suppressed. by doing,
The durability of the bead portion is further improved.

According to a sixth aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the hard rubber is disposed on a lateral side of a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction. The coating rubber is in contact with both the sheet and the coating rubber, between the hard rubber sheet and the coating rubber, or in the tire radial outside of the terminal portion of the bead reinforcing layer on the tire axial outside, or both. And at least the same hardness, more preferably a rubber softer than the coating rubber.

Next, the operation of the pneumatic radial tire according to claim 6 will be described.

By reinforcing the end portion of the bead reinforcing layer with a hard rubber sheet, the compression strain of rubber on the reinforcing layer is suppressed.
Further, by providing soft rubber on the reinforcement layer cord, deformation of the coating rubber of the bead reinforcement layer cord can be further alleviated by suppressing deformation due to hard rubber and absorbing compression deformation by the soft rubber on the cord.

When the end portion of the bead reinforcing layer is reinforced with a hard rubber sheet, the harder the hard rubber sheet is, the more the deformation of the coating rubber of the bead reinforcing layer is suppressed. Concentration of shear strain occurs at the interface of the coated rubber, and the separation failure between the rubber and the rubber is likely to occur. Therefore, not only radially outward of the end of the reinforcing layer,
By interposing soft rubber between the hard rubber sheet and the bead reinforcing layer coating rubber, or at least interposing a rubber of the same hardness as the bead reinforcing layer coating rubber, interfacial shearing by increasing the thickness of the soft rubber or bead reinforcing layer coating rubber. It is more preferable to reduce the distortion and combine it with the deformation suppression by the hard rubber in order to improve the durability of the bead portion.

According to a seventh aspect of the present invention, in the pneumatic radial tire according to any one of the first to sixth aspects, the cord of the bead reinforcing layer has an angle of 30 to 80 with respect to the radial direction. It is characterized by being inclined at an angle within the range of degrees.

Next, the operation of the pneumatic radial tire according to claim 7 will be described.

It is preferable that the cord of the bead reinforcing layer is inclined at an angle in the range of 30 to 80 degrees with respect to the radial direction. When the angle of the cord is less than 30 degrees, the carcass body falls down. At that time, as it approaches the tire radial direction like the steel cord of the carcass layer,
Strain relaxation at the end portion of the bead reinforcing layer due to a change in the angle of the bead reinforcing cord is unlikely to occur, and a large concentration of compressive stress occurs at the cord end.

On the other hand, when the angle of the cord exceeds 80 degrees,
Since the bead reinforcement layer cords are oriented substantially in the circumferential direction, the shear rigidity of the bead reinforcement layer decreases, and the bead suppresses circumferential shear deformation in which the sidewalls are displaced in the rotation direction due to stepping kick when the tire rolls. Since the rim flange is significantly reduced, wear due to circumferential displacement between the rim flange and the tire skin cannot be effectively prevented, and the role as a bead reinforcing layer cannot be sufficiently exhibited.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] As shown in FIG. 1, a pneumatic radial tire 10 of the present embodiment has a pair of bead cores 12 (only one side is shown in FIG. 1) and a pair of bead cores 12. And a carcass 14 straddling in a toroidal shape.

In the present embodiment, the carcass 14 is composed of one carcass layer (carcass ply) 16, but the number of carcass layers 16 may be two or more.

The carcass layer 16 includes a plurality of steel cords (not shown) extending in a substantially radial direction (preferably within ± 10 ° with respect to the radial direction) arranged in parallel with each other. It has a normal structure in which a plurality of steel cords are embedded in a thin coating rubber (not shown).

The carcass layer 16 extends from the bead core 12 of one bead portion 11 to the bead core 1 of the other bead portion 11.
2 and a winding portion 16B wound along the outer peripheral surface of the bead core 12.

The position of the terminal portion 16C of the winding portion 16B of the carcass layer 16 is located on the upper side of the bead core 12 at least inside the tire axial direction outside end of the bead core 12 in the tire axial direction. It is preferably located on the inner side in the tire axial direction from the center, and is further located near the main body portion 16A as shown in FIG. 1 (that is, the carcass layer 16 makes substantially one round around the bead core 12). preferable.

The steel cord of the winding portion 16B is
In the tire manufacturing stage (at least before vulcanization), at least one or more portions are plastically deformed along the outer peripheral surface of the bead core 12, and the steel cord in the product tire is used to return to a straight state. Has not occurred.

Outside the tire of the carcass layer 16, a bead reinforcing layer (so-called chafer) 18 is arranged around the bead core.

The bead reinforcing layers 18 are parallel to each other,
A plurality of cords 19 inclined at an angle in the range of 30 to 80 degrees with respect to the radial direction are covered with rubber (so-called coating rubber) 21. The cord used for the bead reinforcing layer 18 may be a steel cord,
Organic fiber cords such as nylon may be used.

Here, the bead reinforcing layer 18 is disposed adjacent to the bead core 12 along the outer peripheral surface of the carcass layer 16 from the bead core 12 to the terminal portion 18A inside in the tire axial direction. The outer end portion 18 </ b> B extends linearly in a direction away from the bead core 12.

A hard rubber sheet 24 is disposed in close contact with the inner surface of the bead reinforcing layer 18 in the tire axial direction near the end portion 18B on the tire axial direction outside of the bead reinforcing layer 18.

The hard rubber sheet 24 is used for the bead reinforcing layer 1
The hardness is set higher than that of the rubber 21 covering the cord 19 of No. 8.

The hard rubber sheet 24 protrudes outward in the tire radial direction from the end portion 18 B of the bead reinforcing layer 18.

The protrusion d1 of the hard rubber sheet 24 from the terminal portion 18B is preferably set to 25 mm or less when the tire size of the pneumatic radial tire 10 is 285 / 60R22.5. The protrusion amount d1 is a value that is appropriately changed according to the tire size.

The bead portion 11 has a bead core 12
Stiffener 2 that secures the rigidity of bead portion 11 on the tire radial outside of winding portion 16B of carcass layer 16 wound around
0 is provided.

Although not shown, a belt for reinforcing the crown portion of the carcass 14 is provided outside the carcass 14 in the tire radial direction. (Operation) In the pneumatic radial tire 10 of the present embodiment, the steel cord of the carcass layer 16 is habitated by plastic deformation and wound around the outer peripheral surface of the bead core 12,
Since the end portion 16C, which is a source of stress concentration, is arranged so as to be in contact with the bead core 12 which hardly deforms during load rolling, separation failure of rubber in the bead portion 11 starting from the end portion 16C of the carcass layer 16 is prevented. can do.

The bead reinforcing layer 18 disposed outside the carcass layer 16 on the tire is provided with the rim flange 2 at the time of load rolling.
2 prevents wear of the tire skin due to rubbing with 2.

Further, when the bead portion 11 is bent and deformed so as to fall in the direction of the rim flange 22 at the time of load rolling, the main body portion 16A of the carcass layer 16 sinks from the vicinity of the terminal portion 18A of the bead reinforcing layer 18 inward in the tire radial direction. End portion 1 of the bead reinforcing layer 18 on the outer side in the tire axial direction.
A compression force acts on the hard rubber sheet 24 in a direction substantially parallel to the cord direction (the compression direction is the direction of arrow A in FIG. 1).
Is received before the compressive force acts on the end portion 18B of the bead reinforcement layer 18, so that the end portion 18 of the bead reinforcement layer 18 is received.
The stress concentration of B is reduced.

Thus, the end portion 18 of the bead reinforcing layer 18
The occurrence of separation starting from B can be prevented.

Further, the terminal portion 18B of the bead reinforcing layer 18
The side of the bead reinforcing layer 18 is hardly subjected to the force to be pulled out by the internal pressure, and the end portion 18B of the bead reinforcing layer 18 differs from the conventional tire in that the winding portion 16B of the carcass layer 16 (corresponding to the folded portion of the carcass layer of the conventional tire) ) Are not adjacent to each other, and since the cords 19 are arranged inclined with respect to the radial direction, the cords in the bead reinforcing layer 18 are liable to change in angle even when the bead portion 11 undergoes bending deformation during load rolling. This deformation alleviates the concentration of the compressive stress in the radial direction of the terminal portion 18B.

When the tire size of the pneumatic radial tire 10 is 285 / 60R22.5, if the protrusion d1 of the hard rubber sheet 24 from the end portion 18B of the bead reinforcing layer 18 becomes larger than 25 mm, The hard rubber sheet 24 is located on the side of the tire where bending is large,
Since the outer end portion of the hard rubber sheet 24 in the tire radial direction serves as a nucleus for separation, the protrusion amount is preferably 25 mm or less.

When the angle of the cord 19 of the bead reinforcing layer 18 with respect to the radial direction is less than 30 degrees, when the main body 16A of the carcass layer 16 falls down, as in the case of the steel cord of the carcass layer 16, the tire 19 extends in the tire radial direction. Because of the approach, distortion of the end portion 18B of the bead reinforcing layer 18 due to a change in the angle of the cord 19 of the bead reinforcing layer 18 is unlikely to occur, and a large concentration of compressive stress directly occurs at the cord end.

On the other hand, if the angle of the cord 19 exceeds 80 degrees, the shear rigidity of the bead reinforcing layer 18 decreases, and the effect of suppressing circumferential shearing deformation generated at the time of rolling of the tire at the bead portion 11 decreases. Wear due to circumferential displacement between the flange 22 and the tire skin cannot be effectively prevented. [Second Embodiment] A second embodiment of the pneumatic radial tire of the present invention will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 2, in the pneumatic radial tire 10 of the present embodiment, the hard rubber sheet 24 is disposed outside the end portion 18B of the bead reinforcing layer 18 in the tire axial direction.

In this case, the terminal portion 18 of the bead reinforcing layer 18
Although the hard rubber sheet 24 is disposed outside the tire rotation axis direction B in comparison with the first embodiment, the distance between the carcass layer 16 and the main body portion 16A of the carcass layer 16 of the hard rubber disposition portion is larger than that of the first embodiment. Although the effect of suppressing the compressive stress due to bending deformation is relatively small, when the tire skin falls down on the rim flange 22 at the time of the bead portion 11 falling down deformation,
The bead reinforcing layer 18 also has an effect of suppressing the shear strain received by pushing up from the rim flange 22 at the end portion 18B of the bead reinforcing layer 18, and the durability of the bead portion 11 is improved.

The other operations and effects are the same as those of the first embodiment. [Third Embodiment] A third embodiment of the pneumatic radial tire of the present invention will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 3, in the pneumatic radial tire 10 of the present embodiment, the hard rubber sheet 24 is disposed both outside and inside the terminal portion 18B of the bead reinforcing layer 18 in the tire axial direction. It covers the terminal portion 18B and extends outward in the tire radial direction.

In this case, the terminal portion 18B of the bead reinforcing layer 18
By disposing the hard rubber sheets 24 both inside and outside the tire rotation axis direction, the main body portion 16A of the carcass layer 16 described above is provided.
By effectively suppressing both the compressive strain caused by falling down and the shear strain caused by pushing up from the rim flange 22, the durability of the bead portion 11 is further improved. [Fourth Embodiment] A fourth embodiment of the pneumatic radial tire according to the present invention will be described. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 4, in the pneumatic radial tire 10 of the present embodiment, the hard rubber sheet 24 is disposed outside the end portion 18B of the bead reinforcing layer 18 in the tire axial direction. A soft rubber sheet 26 is sandwiched between the and the bead reinforcing layer 18.

The soft rubber sheet 26 is in close contact with the outside of the bead reinforcing layer 18 in the tire axial direction, covers the terminal portion 18B, and extends outward in the tire radial direction. The hardness of the soft rubber sheet 26 is set lower than that of the rubber 21 covering the cord 19.

By reinforcing the end portion 18 B of the bead reinforcing layer 18 with the hard rubber sheet 24, the compression strain of the rubber on the reinforcing layer is suppressed, but the soft rubber sheet 26 is further placed on the cord 19 of the bead reinforcing layer 18. Hard rubber sheet 24
Soft rubber sheet 2 on cord 19 with deformation suppression
6 absorbs the compressive deformation, so that the bead reinforcing layer 18
The distortion of the rubber 21 (coating rubber) of the cord 19 can be reduced. [Other Embodiments] As a modification of the fourth embodiment, a hard rubber sheet 2 as shown in FIGS.
4 and the soft rubber sheet 26 may be arranged. (Test Example) Next, in order to confirm the effect of the present invention, a conventional tire having a tire size of 285 / 60R22.5 and a tire of the embodiment to which the present invention was applied were prepared, and an indoor drum test was performed. Endurance test was performed on the tire.

The tire of Example 1 has the structure shown in FIG. 1, the tire of Example 2 has the structure shown in FIG. 2, the tire of Example 3 has the structure shown in FIG. 3, and the tire of Example 4 Is a tire having a structure shown in FIG. 4, a tire of Example 5 is a tire having a structure shown in FIG. 1, and a conventional tire is a tire having a structure shown in FIG.

Here, in the conventional tire, as shown in FIG. 6, the folded portion 16D of the carcass layer 16 extends outward in the tire radial direction, and the bead reinforcing layer 18 is disposed outside the carcass layer 16. This is a tire having a configuration as described above.

The carcass layers of the tires of Examples 1 to 5 and the conventional example were all (1 × 3 + 9 + 15) × 0.175 mm +
A steel cord having a structure of 1 × 0.15 mm was arranged in parallel at a density of 26 wires per 5 cm (measurement site: around the bead core) and covered with rubber, and the cord direction was substantially set in the radial direction.

Each of the bead reinforcing layers of the tires of Examples 1 to 5 and the conventional example was (1 × 3 + 9 + 15) × 0.175 mm
A steel cord having a structure of + 1 × 0.15 mm is arranged in parallel at a density of 21 wires per 5 cm (measurement site: around the bead core) and covered with rubber, and the cord direction is inclined at 60 degrees to the radial direction. Yes (measurement site:
Terminal portion on the outside in the tire axial direction)

Here, the coating rubber of the steel cord of the bead reinforcing layer of the tires of Examples 1 to 5 and the conventional example has a rubber hardness of 70 degrees (JIS hardness).

The hard rubber sheets of the tires of Examples 1 to 3
The thickness is 2 mm, the rubber hardness is 80 degrees (JIS hardness), and the protrusion amount d1 of the bead reinforcing layer from the terminal portion is 15 mm.

The hard rubber sheet of the tire of Example 4 had a thickness of 2 mm, a rubber hardness of 80 degrees (JIS hardness), a protrusion d1 of the bead reinforcing layer from the end portion of 15 mm, and a soft rubber sheet of The thickness is 2-3mm, the rubber hardness is 60 degrees (JIS hardness), and the protrusion d2 of the bead reinforcing layer from the end portion is 25mm.
It is.

The hard rubber sheet of the tire of Example 5 has a thickness of 2 mm, a rubber hardness of 80 degrees (JIS hardness), and a protrusion d1 of the bead reinforcing layer from the end portion of 30 mm.

In the drum test, an internal pressure of 900 k was applied to the test tire.
After filling with Pa, the steel sheet was pressed on a steel drum having a radius of 1.7 m with a load of 5200 kg, and allowed to run at a speed of 60 km / h until a bead failure (separation) occurred.
The room temperature at that time was 46 ° C.

The evaluation was performed by measuring the running distance until a bead failure occurred, and expressed as an index with the reciprocal of the running distance until the bead failure occurred in the conventional tire being 100. It should be noted that the larger the value, the longer the traveling distance until the bead failure occurs, and the more excellent the durability of the bead.

[0076]

[Table 1]

As a result of the test, Example 1 to which the present invention was applied
It was found that the tires No. to No. 5 significantly increased the traveling distance until the separation occurred in the bead portion, and the durability of the bead portion was greatly improved.

Therefore, it is understood that the pneumatic radial tire to which the present invention is applied is suitable for use as a base tire of a retreaded tire.

Incidentally, in the tire of Example 5,
Separation occurred not at the outer end of the soft rubber sheet in the tire radial direction but at the outer end of the hard rubber sheet in the tire radial direction.

[0080]

As described above, the pneumatic radial tire of the present invention has the above-mentioned structure, and therefore has an excellent effect that the durability of the bead portion can be improved.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a bead portion of a pneumatic radial tire according to a first embodiment of the present invention, and FIG. It is sectional drawing.

FIG. 2 is a sectional view of a bead portion of a pneumatic radial tire according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a bead portion of a pneumatic radial tire according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a bead portion of a pneumatic radial tire according to a fourth embodiment of the present invention.

FIGS. 5A to 5D are cross-sectional views of the vicinity of a terminal portion of a bead reinforcing layer of a pneumatic radial tire according to still another embodiment of the present invention.

FIG. 6 is a sectional view of a bead portion of a pneumatic radial tire according to a conventional example used for a test.

[Explanation of symbols]

 Reference Signs List 10 pneumatic radial tire 11 bead portion 12 bead core 14 carcass 16 carcass layer 18 bead reinforcing layer 18B terminal portion 24 hard rubber sheet (second rubber sheet) 26 soft rubber sheet (first rubber sheet)

Claims (7)

[Claims] A main body extending from a bead core of one bead to a bead core of the other bead; and a winding portion provided continuously with the main body and wound along an outer peripheral surface of the bead core. A carcass comprising at least one carcass layer substantially composed of a plurality of steel cords extending in a radial direction; and a belt provided radially outside the carcass in a tire radial direction and reinforcing a crown portion of the carcass. A pneumatic radial tire, comprising a plurality of cords inclined with respect to a radial direction, including a bead reinforcing layer disposed around the bead core outside the tire of the carcass layer, wherein the tire of the bead reinforcing layer Harder than the coating rubber coating the cord of the bead reinforcing layer on the side of the axially outer end portion A pneumatic radial tire, wherein a rubber sheet is disposed, and the hard rubber sheet is projected outward in the tire radial direction from a terminal portion of the bead reinforcing layer located outside in the tire axial direction. 2. The pneumatic radial tire according to claim 1, wherein the amount of protrusion of the hard rubber sheet from a terminal portion of the bead reinforcing layer on the outside in the tire axial direction is 25 mm or less. 3. The pneumatic radial tire according to claim 1, wherein the hard rubber sheet is disposed inside the bead reinforcing layer in the tire axial direction. 4. The pneumatic radial tire according to claim 1, wherein the hard rubber sheet is disposed outside the bead reinforcing layer in the tire axial direction. 5. The hard rubber sheet is disposed both outside and inside the bead reinforcing layer in the tire axial direction, and covers a terminal portion of the bead reinforcing layer outside the tire axial direction. The pneumatic radial tire according to claim 1 or 2, wherein 6. A contact between the hard rubber sheet and the coating rubber, which is in contact with both the hard rubber sheet and the coating rubber disposed on a side of a terminal portion of the bead reinforcing layer on the outer side in the tire axial direction, Or, in the tire radial direction outside of the end portion of the bead reinforcing layer in the tire axial direction, or both, at least the same hardness as the coating rubber, more preferably having a rubber softer than the coating rubber. The pneumatic radial tire according to claim 1 or 2, wherein: 7. The cord according to claim 1, wherein the cord of the bead reinforcing layer is inclined at an angle in a range of 30 to 80 degrees with respect to a radial direction.
The pneumatic radial tire according to the item.